1. Field of the Invention
The invention relates to a method of processing a television picture signal including video and graphic information, said processing comprising the step of storing the television picture in a picture memory. The invention also relates to a television receiver adapted to carry out such a method.
2. Description of the Related Art
Current television receivers show an increased use of digital signal processing circuits for features, such as noise reduction and/or flicker reduction. Generally, the receivers have a picture memory for that purpose. Television receivers also have additional features, such as teletext reception, sophisticated menu-driven control systems, multilingual subtitling, electronic TV-Guide facilities, etc. These additional features require on-screen-display of graphic information. Often, this graphic information is generated by character-based graphics devices which require a moderate memory capacity. However, there is a trend towards enhanced graphics devices which define graphic information on a pixel-by-pixel basis and require a large memory capacity.
Needless to say, that it is important to reduce the memory capacity in such television receivers, for example, by using a shared memory for the various functions. A television receiver having such a shared memory is disclosed in U.S. Pat. No. 5,119,200. This prior art comprises a picture memory for storing the received video signal as well as the locally generated graphics (teletext) signal. The receiver utilizes the fact that a pixel on the screen either represents video information or graphic information. One bit per pixel is stored in the memory to indicate the type of information. The prior-art receiver allows the video information in the memory to be refreshed and processed at the field or frame rate without affecting the stored graphic information.